In the relevant art, a gypsum-cement, gypsum-resin, or gypsum-cement-resin compositions are taught in which the water resistance of gypsum is improved. Such compositions are disclosed in Japanese laid-open Patent Application Nos. 49-52823 and 53-144934. In particular, the gypsum-cement-resin composition disclosed in Japanese examined and published Patent Application No.58-30257 provides sufficient water resistance for a short time, around one day. However, when the water resistance test is performed over a longer period of time, one week or longer, a problem arises, namely the composition swells.
In the gypsum-cement-resin composition described in Japanese laid-open Patent Application No. 48-43416, the content of the cement is of a larger ratio than that of the gypsum. Such a composition provides fluidity, water resistance and strength over a long period of time, but not without shortcomings. Primarily, the composition is susceptible to cracking over time.
To solve the aforementioned problems, Japanese laid-open Patent Application No. 6-128009 discloses a floor finish composition which can be applied in a short time and provides water resistance and crack prevention. The composition is mainly composed of 85 parts by weight of .alpha.-type hemihydrate gypsum, 15 parts by weight of white cement, 10 parts by weight of white pigment and 40 parts by weight of acrylic emulsion containing 57% of solid content. The composition provides a compression strength of about 80 kg/cm.sup.2 two hours after the composition is applied. Several hours after the composition is applied to the floor, it can provide strength such that people can walk on the floor without any problem. The composition reduces the time for application, is superior in water resistance and fluidity, and is suitable as a self-leveling material and foundation preparing and finishing material.
The floor finish composition disclosed in Japanese laid-open Patent Application No. 6-128009 has superior fluidity, water resistance and early strength for its use on the floor. However, when the composition is exposed to solvents, oil, or the like, it tends to bulge. The strength of the composition is thus deteriorated such that the composition fails to bear use over a long period of time.
For example, in a gas station, a floor finish composition requires a resistance against solvents, oil, and the like, and a strength to bear a vehicle's weight. Especially in the winter season, a strength of at least about 150 kg/cm.sup.2 is required so that the floor is not damaged by vehicles with tire chains. The aforementioned composition disclosed in 6-128009 indicates a relatively high compression strength of about 80 kg/cm.sup.2 two hours after the composition is applied to the floor. However, on the next day the composition provides a compression strength of only about 90 kg/cm.sup.2. The ratio of increase or rise in strength relative to time is insufficient. In general, when a floor composition is applied, it should set and have the requisite strength so that the floor can be used no later than the next day. Therefore, this conventional floor finish composition is not suited for the floor or the gas station floor.